Photographic antihalation layer made from alloxan



, W WW; 5. E. SHEPPARD mm. I J B PHOTOGRAPHIC ANTIHALATION LAYER MADE FROM ALLOXAN Filed April 12, 1939 GELATIN ANTI- HALATION LAYER CONTAINING A DYE MADE FROM ALLOXAN EMULSION f GELATBN ANTI-HALATBDN LAYER cowmmme Q A ms MADE FROM mmmw A u a @ELA'WN @VERCOA'WM LAYER cowmmlwa A DYE MADE FROM .EaLLQkAFE w 3 EMULSION M auwom ZjrWMTo M Sum/mm BShwumd;

mbm mam Patented Dec. 19, 1939 itar rice PHOTOGRAPHIO ANTIHALATION LAYER MADE FROM ALLOXAN New Jersey Application April 12,1939, Serial No. 267,478

13 Claims.

This invention relates to antihalation layers for photographic film.

This application is a continuation-in-part of our application Serial No, 102,546, filed September 25, 1936.

The purpose of providing films with antihalation layers is well known in the photographic art. When a photographic film is exposed, there is a tendency for light to be reflected from the surface of the film support or other layer of the film and to produce on the sensitive emulsion layer, according to its intensity, halos surrounding brighter parts of the image. This effect is known as halation and it is customary to coat the rear surface of the support with a coloring material which absorbs the light and prevents a reflection onto the sensitive layer. The coloring matter designed for antihalation purposes must ordinarily be removed during or after processing the sensitive element.

It is obvious that the coloring matter used for this purpose should be removed as completely as possible during processing of the film. Some dyes which are readily removed in an alkaline solution, such as a photographic developer, have a tendency to discolor the developer to such an extent that it is rendered useless for further development. It is desirable to maintain the developing solution in a pure condition so that it may be used to develop large amounts of film.

It is, therefore, an object of the present invention to provide an antihalation layer having a dye which is readily decolorized and removed in the processing baths. It is a further object to provide an antihalation dye which is produced by reaction with constitutents of the gelatine in which it is located. Other objects will appear from the following description of our invention.

These objects are accomplished by incorporating in gelatin certain compounds reactive with gelatine to produce a dye, such as alloxan, alloxantin, and triketohydrindene hydrate. The dyes formed from these compounds are believed to be analogues of murexide, which is the ammonium salt of purpuric acid.

In the accompanying drawing we have shown a number of enlarged sectional views. of photographic film coated with antihalation layers according to our invention.

In the drawing:

Fig. 1 is a sectional view of a film having an antihalation layer on the rear surface of the support;

Fig. 2 is a sectional view of a film having an antihalation layer between the emulsion layer and the support; and

Fig. 3 is a sectional View of a film having an antihalation layer coated over the emulsion layer.

We have found that certain dyes analogous to murexide may be produced in a gelatine layer by incorporating the precursors of the dyes in the gelatin. By precursors we mean the carbocyclic or heterocyclic nuclei used to form the dyes,

such as triketohydrindenehydrate or alloxan. In

this manner a quantity of alloxan, for example, may be incorporated with gelatin to produce a coloring matter which is identical with, or similar to, the dyes formed before incorporation in the gelatin. The coloring matter formed in this way is, we believe, produced by condensation of the precursor of the dye with one or more of the amino groups of the gelatin, although we do not wish to be limited to this explanation of the chemical reaction involved. The discovery of the fact that coloring matter can be formed by incorporation of compounds of this type in gelatin is not part of our invention. We believe, however, that we are the first to find that dyes formed in this way are similar to dyes of the murexide type, and that these dyes may be used for antihalation purposes and may be bleached in ordinary photograhic processing baths.

Compounds which we have found suitable for use in producing antihalation dyes are alloxan, alloxantin, their alkyl derivatives such as methyl alloxan and tetramethyl alloxantin, and triketohydrindene hydrate.

The structure of alloxan may be represented as follows:

\NHCO Alloxantin is formed by reduction of alloxan, and has the following structural formula:

When these compounds are mixed with gelatin, the solution is normally colorless. However,

All)

when the pH of the solution is properly adjusted, the color forms on drying the gelatin. We have found that at pH 7 or higher, no color is ordinarily formed, even on drying, while color is formed below pH 7 on drying, whether or not the gelatin contains a large or small amount of ash. The

ash content of the gelatin does, however, affect the color of the resulting dye.

Typical results on drying a mixture of depH of gelatin-alloxan mixture Color (on drying) Orange. Slight color on edge.

Colorless.

When the pH was adjusted with NH4OH or triethanolarnine instead of NaOH, similar results were obtained. The difierence in color resulting from the use of un-deashed gelatin is believed to be due to the presence of calcium in the ash.

The dyes produced in this way have a region of maximum light absorption at about 500 to 522 millimicrons. The absorption maximum is shifted by a change in pH of the solution and by the ash content of the gelatin. An increase in pH tends to shift the absorption maxima toward the shorter wavelength region. At pH 4.6, for example, an absorption maximum was found to lie at 522, whereas at pH 6.0 it was at 514.

The following examples, which are illustrative only, indicate methods of forming antihalation layers according to our invention.

Example 1 0.28 gram of alloxan was dissolved in 50 cc. of water and the solution added to 7 grams of gelatin in 50 cc. of water. The pH was adjusted to 4.8 with NaOH. The mixture, which was colorless, was coated on a glass plate and permitted to dry. Upon drying, the coating attained a red color having a maximum light absorption at about 522 mu.

Example 2 1.25 grams of triketohydrindenehydrate were dissolved in 50 cc. of water and the solution. was added to '7 grams of gelatin in 50 cc. of water, and found to have a pH of 4.8. About 25 cc. of this mixture was coated on a film support subbed with cellulose nitrate. The skin which had a reddish-purple color on drying, showed marked absorption at 410 mu and 580 mu.

The anti-halation layers made according to our invention may be used in various ways to coat photographic film on paper. In the accompanying drawing, we have shown in Fig. l a section view of the usual film construction in which ill represents a transparent support of cellulose nitrate, cellulose acetate, synthetic resin or other suitable material coated with an emulsion layer II. On the opposite side of the support l there is coated a gelatin layer I2 containing alloxan or another of the precursors used according to our invention. Fig. 2 represents another type of film in which the anti-halation layer [2 is coated between the support 10 and the emulsion layer II. An anti-halation layer of this type might be used with a paper or other opaque support. Fig.8 represents a further type of film in which the anti-halation layer I2 is coated over the emulsion layer I, the emulsion lay H being coated on the support ill. This latter type of film is designed for use in the exposure of the sensitive emulsion layer through the support and in this type as well as in the other types of film it is highly desirable to remove the anti-halation layer during processing of the film or paper. The dye layer coated over the support as in Fig. 3 may also serve as a filter layer for exposure of the sensitive emulsion through the layer l2.

Where we refer in the claims to alloxans and alloxantins, it is to be understood that we intend to include the derivatives of alloxan and alloxantins such as methyl alloxan and tetramethylalloxantin, referred to in the specification. The examples of the dye compounds and the methods of using them referred to in the above specification are by way of il ustration only and it is to be understood that our invention is to be taken as limited only by the scope of the appended claims.

What we claim:

1. A photographic element comprising a support having thereon a sensitive emulsion layer, and a layer of unsensitized gelatin. containing a compound selected from the group consisting of alloxans, alloxantins and triketohydrindenehydrate.

2. A photographic element comprising a support having thereof a sensitive emulsion layer, and a layer of unsensitized gelatin on said support having a pH less than seven and containing alloxan uniformly mixed therewith.

3. A photographic element comprising a sup port having thereon a sensitive emulsion layer, and a layer of unsensitized gelatin on said support having a pH less than seven and containing alloxantin uniformly mixed therewith.

4. A photographic element comprising a support having thereon a sensitive emulsion layer, and a layer of unsensitized gelatin on said support having a pH less than seven and containing triketohydrindenehydrate uni f o r ml y mixed therewith.

5. A photographic element comprising a sunport having thereon a gelatino-silver halide emulsion layer, and a layer of unsensitized gelatin on said support having a pH less than seven and containing the reaction product of gelatin and a compound selected from the group consisting of alloxans, alloxantins and triketohydrindenehydrate.

6. A photographic element comprising a transparent support. a gelatino-silver ha ide emulsion on one side of said support and on the opposite side of said support a layer of gelatin having a pH less than seven and containing the reaction product of gelatin and a compound selected from the group consisting of alloxans, alloxantins and triketohydrindenehydrate.

'7. A photographic film comprising a transparent support, a gelatino-silver halide emulsion on one side of said support and on the opposite side iii of said support a layer of gelatin having a pH less than seven and containing the reaction product of gelatin and alloxan.

8. A photographic film comprising a transparent support, a gelatino-silver halide emulsion on one side of said support and on the opposite side of said support a layer of gelatin having a pH less than seven and containing the reaction product of gelatin and alloxantin.

9. A photographic film comprising a transparent support, a gelatino-silver halide emulsion on one side of said support and on the opposite side of said support a layer of gelatin having a pH less than seven and containing the reaction prodnot of gelatin and triketohydrindenehydrate.

10. The method of producing a photographic antihalation layer which comprises mixing with gelatin having a pH less than seven, a compound selected from the group consisting of alloxans, alloxantins and triketohydrindenehydrate to form a substantially colorless gelatin solution, coating the solution on a photographic support, and drying the solution to form a colored gelatin film.

11. The method of forming a photographic antihalation layer which comprises incorporating alloxan in gelatin having a pH less than seven to form a substantially colorless gelatin solution, coatin the solution on a photographic support, and drying the solution to form a colored gelatin layer.

12. The method of forming a photographic antihalation layer which comprises incorporating alloxantin in gelatin having a pH less than seven to form a substantially colorless gelatin solution, coating the solution on a photographic support; and drying the solution to form a colored gelatin layer.

13. The method of forming a photographic antihalation layer which comprises incorporating triketohydrindenehydrate in gelatin having a pH less than seven to form a substantially colorless gelatin solution, coating the solution on a photographic support, and drying the solution to form a colored gelatin layer.

SAMUEL E. SHEPPARD. ROBERT C. HOUCK. 

